1. Technical Field
This invention relates to fluid control by water gates and more particularly, to pivoted gates responsive to water pressure.
2. Background Art
Prior patents by the present invent or have addressed preventing surface storm waters from entering and flooding lower levels of buildings or underground garages (U.S. Pat. No. 6,623,209) and preventing storm waters from storm sewers back flowing through street gutters into surface streets (U.S. Pat. No. 7,101,114). These inventions do not address the problem of surface storm waters entering and flooding underground tunnels and chambers through ventilation ducts connecting the underground chambers or tunnels to air at ground surface. Such chambers and tunnels include, without limitation, underground transportation tunnels for road vehicles, trains, and subways, and underground chambers, such as associated with a complex of connecting tunnels and shafts, for example as used for such things as underground hydroelectric-power plants, or with underground utilities which require ventilation, such as underground transformer rooms. In the case of subway systems, solutions have been suggested for reducing entrance of runoff water from street level grate openings through the ventilation ducts down into the underground systems, such as raising the subway grates above sidewalk level, but these are often not only costly to implement for each sidewalk grating area but also largely impracticable because much of the available sidewalk area available for pedestrians, already at a premium, is sacrificed to the solution.